Positioning method for a drilling head

ABSTRACT

Positioning method of a bit or a drill head ( 22 ) of a drilling device which drills an underground hole in which method devices which measure the situation of the drill head and/or receiving devices of signals which have been sent from elsewhere and are related to the mentioned measuring and equipment ( 3, 4 ) in order to convert the measurement data into a signal form which can be sent onto the ground surface, a possible battery ( 10 ) to be a power source and devices in order to send the signal from the drilling head ( 22 ), are located to the drilling head, most advantageously into a protected unit ( 6 ). The positioning data of the drill head ( 22 ) is clarified with the help of a signal sent from the ground surface so that the overground position from which sent signal is at its strongest when it is being received in the drill head ( 22 ) is searched and the position of the drill head is determined from this position to be located directly underneath and the depth position of the drill head ( 22 ) is determined as weakening of the signal which has been sent from the ground surface to the drill head ( 22 ) wherein the experimentally defined weakening of the signal per a ground metre is used in order to determine the depth position and the data detected at the drill head ( 22 ) are sent to the ground surface either by radio along a drill rod pipe ( 9 ) or from the drill head ( 22 ) through the ground onto the ground surface the shortest way possible.

The invention relates to a positioning method of a bit or a drilling head of a drilling device which drills an underground hole in which method sensors which indicate the angles of direction of at least the progression of the drill head, an equipment in order to convert the sensor data into a signal form which can be sent onto the ground surface, a battery to be a power source and a radio transmitter and an antenna are located to the drill head, most advantageously into a protected unit.

It is already known that regarding horizontal, underground drilling a guide hole is drilled underneath the ground for the water-, sewer- and electric cable pipes by pushing iron pipes hydraulically underneath the ground. After that a bigger pipe is pulled back along the same hole. When one drills in this way near the ground surface, the position of the bit can be defined with the help of a radio transmitter located at the head and with the help of a receiver located on the ground, the patent specification U.S. Pat. No. 6,417,666 being an example. This method however functions only close to the ground surface. The working distance is normally less than ten metres. By bringing more power underneath the ground with the help of cables, this distance can be increased at most up to 50 metres. During the horizontal drilling pressurized bentonite is used as a lubricant and metal tubes which can be added sequentially are used so that the usage of cables is nearly impossible.

The usage of the horizontal drilling equipment in order to make holes for the ground heat pipes in a soft ground requires the measuring of the location of the head of the drill. With the known horizontal drilling equipment the movement of the drill can be controlled if on the ground it is known where the bit is located during the drilling. The control occurs with a chisel like bit which is installed at the end of the first pipe. When the pipe is being rotated, the bit moves normally directly. When the bit is not being rotated, the pipe turns directed by a chisel when the pipe is being pushed forward. A ground heat hole made with horizontal drilling devices would be considerably more profitable than a rock drill hole. The ground heat pipes are drilled deeper than the water-, sewer- and electricity pipes related to the municipal engineering.

Vertical holes needed in the ground heat engineering can be measured with the current prior art only very close to the surface of the ground. Although the location of the vertical pipes is not exactly as important as the location of the horizontal pipes, drillings cannot be performed at random. The same problem exists in the metallic supporting pipes used in the foundation of houses. In some cases the pipes have turned and have risen back onto the surface of the ground.

The work which has been done in this way must be done over because during the work one does not know the location of the pipe underground. In these cases the directness of the pipe, which has an effect on the load bearing capacity of the base of the house, has been measured afterwards and the performed work must be rejected. The data regarding the position of the pipes thus already during the work is economically important.

In the presented method the location data of the drilling head can be sent onto the ground surface already during the drilling and thus a clear improvement can be achieved regarding the current prior art. What has been described in the claims is characteristic of the method according to the invention.

The following things can be mentioned as advantages of the method according to the invention:

The distance of the drilling head can be found out by calculating the amount of the drilling pipes having a standard measure.

-   -   The depth of the drilling head can be found out from the         weakening data of the signal received at the drilling head.     -   The position of the drilling head can be found out with a         bidirectional tilt sensor. If the tilt angles x and y are at         zero, the drill is in an upright position.     -   The angle of rotation of the steering shovel can be found out         with a tilt sensor.     -   The data from the sensors is sent onto the ground surface with a         radio signal without an isolated cable. Because the metallic         pipe will always appear on the ground surface, the depth of the         drill head is no longer important regarding the measuring power.     -   The location of the bit can be found out on the ground surface         by using a principle of the strongest signal.     -   During the pipe changing the drill bit is at an unoperated state         in which case the angular measurements are accurate.     -   The weakening of the radio signal in a metallic pipe is a lot         less than through the ground or air. This property is very         important regarding battery-driven devices.     -   Although the iron pipe is not isolated from the ground, the         signal runs easily along an iron pipe which conducts electricity         well such as it is usual for electricity. Data transfer through         water and wet ground has so far been impossible because of         extensive weakening.     -   The underground real time measurement data enables the control         of the pipe and the documentation regarding the hole.     -   The bidirectional data transfer enables the control of the         sensors and the transmitter only exactly at the right moment.         The usage of the device and the changing of the battery is under         control.

In the following the invention is described more detailed by referring to the accompanying drawing in which

FIG. 1 shows horizontal drilling during which the pipes are pushed sequentially into the ground.

FIG. 2 shows a device unit which can be located at the drilling head according to the invention.

FIG. 3 shows an overground device unit.

FIG. 4 shows a positioning system which uses overground transmitters.

FIG. 5 shows the positioning of the drill head of an underground pipe with a moveable equipment.

FIG. 6 shows diagrammatically a device unit equipped with a display panel.

The horizontal drilling situation is shown diagrammatically in the FIG. 1 in which horizontal drilling situation a pipe 9 or a drill rod equipped with a head piece 22 is pushed sequentially first into the ground with the help of a power unit, such as an excavator in which pipe or a drill rod the head piece 22 is a slanting surface, so called head shovel. When the drilling proceeds pipes 9 are added after each other. Usually the horizontal drilling hole makes a gradual turn in which case the drill head must be controlled. If the drill head and the whole sequential piping 9 is being rotated, the drill head goes directly forward in spite of a diagonal head surface. If the rotating is stopped, the slanting head surface begins to change the direction. The rotating is stopped in such position in which the slanting surface directs the drilling head into the desired direction. The unit 21 related to the localization of the drill head is located at the drill head. The flange 20 related to the rotating and pushing is located in the backmost pipe 9 located on the ground surface.

The functioning of the underground positioning device is described with the help of the FIG. 2. The device comprises first a sensor and a transmitter unit 21 located at the head of the drilling device. A such known micromechanical tilt sensor 1 is located at the underground device. It measures the tilt of the pipe in the longitudinal and horizontal direction. A magnetic compass 2, which measures the direction of the head of the pipe in relation to the magnetic north pole, also functions as a sensor. The sensor signals are converted into a serial bus message form with a microprocessor 3. The serial bus message is converted for the radio with a frequency modulator 4. A FSK-modulated audio signal controls a low-power radio transmitter 5 functioning at a HF-frequency. The antenna 7 of the transmitter is connected to the metallic casing 9 of the drill. The measuring device is located in an isolated casing 6. The iron pipe 9 is formed of pieces of 4 metres which have tight taper threads 8.

There is the overground part of the positioning system in the FIG. 3. In the overground part the antenna 11 of the radio receiver 12 is connected to a metallic pipe 9. The audio signal received from the radio is demodulated in the FSK-detector 13 back to a serial bus data. The serial bus data is decoded into measurement data in a microprocessor 14. The microprocessor also measures the length of the pipe with a pulse sensor 15, cycles and the synchronization of the tilt with a cycle sensor 16. The results are shown with a localized display unit 17. With the help of a pushing device and a rotating motor 18 the drilling can be controlled when one knows the location of the head of the drill. The measurement data is saved into the memory 19. Field tests regarding the method have been made in a wet ground with which tests the functionality of the invention has been ensured.

Measurements have been made at several various frequencies. The measuring functions at least at the frequency of 1-70 MHz. In a dry ground more than −70 dBm power is needed and in a very wet ground +16 dBm per 100 metres is needed.

In another execution form shown in the FIG. 4 the positioning method of a drill bit or a drill head of a drilling device drilling an underground hole is such in which a listening receiver 33 is placed to the drill head which receiver receives signals from the ground surface sent by at least three transmitters 30, 31, 32 located in various places, further the drill head comprises a unit which calculates the location data of the drill head on the strength of field strengths of these at least three transmissions. As an additional location data the length data of the drill rod which is fed into the ground can be sent in this case also in the way according to the invention along the drill rod to the drill head. This helps also to specify the determining of the position of the drill head. Also in this case the drill head still has a battery as a power source, a radio transmitter 34 and, an antenna. The signal sent by the radio transmitter 34 located at the drill head is transferred to the metallic drilling pipe/rod 35 of the drilling device functioning as an antenna in which case the mentioned signal is received on the ground surface from the mentioned drill rod by attaching the antenna of the receiving unit to the mentioned drill rod. The used triangulation becomes more accurate if the transmitters 30-32 located on the ground surface are located from each other approximately at the same distance as the sensor 33 receiving transmitting signals. During the measuring the known distance of the sensor from the starting point of the drilling is additionally utilized.

By using timed signals to various transmitters 30-32, by using transmitters which function with the mains current and by using powerful, short-duration transmitting power, additional length can be considerably gained regarding the measurable positioning distance and positioning depth compared to the access radius of the signal when one uses low-power battery transmitters. Earlier the signal has been sent from the end of the pipe onto the ground surface with battery-driven transmitters. This method does not however function with deeper depths of the drilling head. During the receiving no extensive power is needed and the measured field strengths at the sensor 33 can be sent with a low-power radio 34 along a pipe 35.

The locating of the power tool 23 to the overground starting point of the pipe to be pushed into the ground is shown in the FIG. 5 from which starting point the pushing and the rotating of the pipe occurs with the help of a power tool 23. In the situation of the FIG. 5 the pipe 9 has been pushed so far into the ground that the location of the drill head 22 must be observed. In this case the person 24 walks with the measuring unit 25 on the ground surface at the assumed point of the drill head 22. The unit of measurement 25 sends a strong signal downwards and the sensor-, receiving- and transmitting unit 21 located at the drill head 22 receives this signal and sends the strength data of the signal to the starting point to the machine operator along Rx1-Rx2 the drill rod pipe 9.

The machine operator has a display panel 26, such as the person 24 has. The displays are parallel displays so that a signal comes from the display panel 26 of the machine operator to the display panel 26 of the measuring unit 25 carried by the person 24 and the mentioned display panels thus show the same positioning data. With this arrangement the person 24 can search for a place from which the strongest signal comes to the drill head. When the place has been found, the drill head 22 is located directly underneath this place. From the strength of the signal received by the drill head 22 at this place one can determine what the thickness of the ground is, in other words at which depth the drill head 22 is located. The sent signal becomes weaker according to the thickness of the ground and does not depend on the quality of the ground much. The weakening of the signal per a ground metre is predetermined with experiments and this information is being used. The person 24 can thus proceed without a contact to the machine operator and carries the measuring unit 25 above the drill head 22 when the pipe 9 is being pushed into the ground. All the collected data which corresponds to the passed distance is saved on the computer of the measuring unit 25. The person 24 can carry a powerful enough power source with him/her so that a strong signal can be sent under the ground.

The machine operator can see on his display panel 26 for example the depth position, tilt position, rotational position and the temperature of the drilling head 22 when the unit 21 located at the drilling head 22 and related to the positioning sends also this data as a radio signal along the drill rod 9 to the display panel unit 26 of the machine operator. The gaining of this data from the sensors in question and the sending does not exactly increase the power of the battery needed at the drill head 22. The machine operator has a pre-planned drilling track for the pipe 9 and if the direction of the drill head 22 deviates from this, he controls the drill head 22 to turn to the right track.

FIG. 6 shows the display panel 26 and other devices and functional units related to it. It comprises a display screen 27, a computer CPU 28, a battery 29, a GPS- locator 37, a memory 38, an antenna 39, GSM 40 and a transmitter 41 in order to send a signal both to the ground and to the drill rod. The display screen 27 for example shows the position of the pipe and thus the deviation from the thought location at this point.

The positioning shown by the FIG. 5 can also occur in an alternative way by deviating a little bit from the above described way in which case no signal is being sent to the machine operator along the drill rod 9. At the drill head 22 there is a RFID-coil with its external devices, such as tilt-, rotation- and temperature sensors and a CPU in which case in this case the person 24 sends from the ground surface powerful enough carrier wave, for example 32 kHz, with the transmitter 41 of the measuring unit 25 under the ground at one or several locations Tx1-Tx4 and at least one RFID-unit at the drill head 22 excites and sends modulated wave back to the measuring unit 25. With the help of CPU for example the first 10 bits of the modulated signal which is sent back are adjusted to describe the amplitude of the received signal, the next 10 bits are adjusted to describe the information given by the roll transformer of the drill head, the next 10 bits are adjusted to describe the rotational position of the drill head and the next 10 bits are adjusted to describe the temperature. Also in this case the person 24 has a display- and device unit according to the FIG. 6 and the machine operator has his own. Now the data of the display panel of the person 24 is for it's part sent to the display panel 26 of the machine operator. The depth position of the drill head 22 can be gained also in this case from the weakening of the signal per a ground metre of which one has experimental results and metre amounts corresponding to them. 

1. Positioning method of a bit or a drill head (22) of a drilling device which drills an underground hole in which method devices which measure the situation of the drill head and/or receiving devices of signals which have been sent from elsewhere and are related to the mentioned measuring and equipment (3, 4) in order to convert the measurement data into a signal form which can be sent onto the ground surface, a possible battery (10) to be a power source and devices in order to send the signal from the drill head (22), are located to the drilling head, most advantageously into a protected unit (6), characterized in that the positioning data of the drill head (22) is clarified with the help of a signal sent from the ground surface so that the overground position from which sent signal is at its strongest when it is being received in the drill head (22) is searched and the position of the drill head is determined from this position to be located directly underneath and the depth position of the drill head (22) is determined as weakening of the signal which has been sent from the ground surface to the drill head (22) wherein the experimentally defined weakening of the signal per a ground metre is used in order to determine the depth position and the data detected at the drill head (22) are sent to the ground surface either by radio along a drill rod pipe (9) or from the drill head (22) through the ground onto the ground surface the shortest way possible.
 2. Method according to the claim 1, characterized in that the equipment (25),(26) carried by the person (24) and performing positioning and the display equipment (26) of the machine operator working at the starting point send signal data in a bi-directional way.
 3. Method according to the claim 1, characterized in that overground position: track of the positioning of the drilling head (22) are indicated with a GPS- equipment.
 4. Method according to the claim 1, characterized in that a RFID-unit is placed at the drilling head which unit receives a carrier wave sent from the ground surface and sends the carrier wave in a modulated form when the modulations include signal and sensor data of the drilling head (22) when the modulated carrier wave can be received on the ground surface and from the modulations the data sent by the drilling head can be solved.
 5. Method according to the claim 1, characterized in that during the drilling based on the rotating of the drill rod (9) the angle of rotation of the drilling head is measured during the horizontal drilling by using an angle sensor which is located at the drilling head and is based on gravity and during the vertical drilling the angle of rotation of the drilling head is measured by utilizing the indication of the sensor detecting the direction of the magnetic field of the earth.
 6. Method according to the claim 1, characterized in that the person (24) moves forward with the measuring device (25) on the ground surface above the detected location of the drilling head (22). 